In the field of clinical and diagnostic analyses, swabs for collecting biological specimens of organic material are known, consisting essentially of a cylindrical rod around one end of which, known as the tip, is wrapped a wad of fibre such as rayon or a natural fibre such as cotton, with hydrophilic properties to allow rapid absorption of the quantity of specimen to be collected and tested. Stable adherence of the fibre wrapped around the tip of the rod is generally achieved by gluing.
Usually, especially if the specimen is to be examined by culturing the microorganisms gathered with the collection, a swab is immersed in a test-tube containing culture medium immediately after collection for appropriate conservation of the specimen during storage and/or transport thereof to the analytical laboratory.
An example of this type of device is given in patent EP0643131 by the same Applicant and refers to a swab for collecting and in vitro transporting specimens, of the type comprising a test-tube with culture medium in gel form and a rod carrying at one end a stopper for sealing the test-tube and at the opposite end means for collecting said specimen, for example a wad of fibre wrapped around the tip of the rod, to be dipped into the culture medium.
The tip of the cylindrical rod, generally manufactured from essentially rigid material such as plastic, for example by extrusion, commonly presents a truncating cut which would make it difficult to insert the swab rod into the cavities (oral, nasal, ocular or rectal, urethral, vaginal etc.) of the patient from whom the specimen is taken, if the tip is not adequately protected. Therefore, the wad of hydrophilic fibre wrapped around said truncated end must not only contain sufficient material to allow absorption of the specimen in the desired quantity, in general 100 microliters, but must also have a sufficiently thick and rounded shape to sheathe the edge of the truncated end so that it cannot cause damage or irritation to the patient during specimen collection. For this reason the fibre wad is wrapped around the tip of the rod in a rounded shape, typically developing into an ogive or similar shape so that it gradually becomes thicker towards the end of the rod thus reaching maximum thickness and therefore maximum protective effect, precisely around the truncated end. A wad of such a shape, while protecting the patient from any risk of contact with said truncated end of the rod, results in a number of drawbacks. The main one is that the thickness of the wad, because of the hydrophilic nature of the fibre, leads to penetration of collected liquid specimen into the mass of said wad. As, for practical reasons, the sample is released from the swab at the moment of analysis by simply gripping the rod of the swab and delicately sliding its tip and hence the fibre impregnated with liquid, along for example a petri dish with culture medium, in practice by spreading the specimen onto this latter (swabbing), even if this operation is repeated and is careful, it does not enable the entire volume e.g. the 100 ml of absorbed specimen to be released, because that part of it which has penetrated into the interior of the wad in the direction of its tip cannot be pressed out towards the surface and hence released by the swab during this operation.
Due to this defect, on average only about 40% of the liquid specimen collected can in practice be recovered for analysis. Such loss of specimen translates inevitably into reduced sensitivity of analysis and increased false negatives. In this respect, referring to the aforementioned average specimen loss after swabbing the swab, by testing only the 40 microliters released for swabbing out of the 100 microliters of specimen initially collected, it becomes difficult to establish whether a negative test effectively refers to the absence of the microorganism sought or rather to its non- or insufficient transfer from swab to test plate.
A further problem derived from the bulky fibre wad of a swab of the known art is particularly evident for example in the case of urethral or ocular use of said swab. In these and other particular applications it would actually be even more desirable to be able to minimize swab thickness and hence patient discomfort during collection.